1. Field of the Invention
This invention relates to a liquid discharge head for discharging desired liquid by the creation of a bubble occurring by heat energy being caused to act on the liquid, and a method of manufacturing such liquid discharge head. Particularly the present invention relates to a method of manufacturing a liquid discharge head having a movable member displaced by the utilization of the creation of a bubble, a liquid discharge head manufactured by the same method, and a method of manufacturing a minute mechanical apparatus.
Also, the present invention can be applied to apparatuses such as a printer for effecting recording on recording mediums such as paper, yarn, fiber, cloth, metals, plastics, glass wood and ceramics, a copier, a facsimile apparatus having a communication system and a word processor having a printer portion, and an industrial recording apparatus compositely combined with various processing apparatuses.
The term xe2x80x9crecordingxe2x80x9d in the present invention means not only imparting meaningful images such as characters and figures to the recording mediums, but also imparting meaningless images such as patterns to the recording mediums.
2. Related Background Art
FIG. 12 of the accompanying drawings is a partly broken away perspective view showing a liquid discharge head according to the prior art.
As shown in FIG. 12, the liquid discharge head according to the prior art has a substrate 1004 on which a plurality of heaters 1005 which are bubble creating elements for giving head energy for creating bubbles in liquid are provided in parallel, and a top plate 1001 joined onto this substrate 1004.
The substrate 1004 comprises a base body of silicon or the like on which silicon oxide film or silicon nitride film are formed for the purposes of insulation and heat accumulation, and electrical resistance layers and wiring electrodes constituting the heaters 1005 being patterned thereon. By a voltage being applied from these wiring electrodes to the electrical resistance layers to thereby flow an electric current to the electrical resistance layers, the heaters 1005 generate heat. On the substrate 1004, there are provided packaging electrodes 1003 to which external terminals (not shown) for supplying an electric current to the heaters 1005 are connected.
The top plate 1001 is for constituting a plurality of liquid flow paths 1007 corresponding to the heaters 1005 and a common liquid chamber 1010 for supplying the liquid to the liquid flow paths 1007, and is integrally provided with flow path side walls 1001a extending from the ceiling portion thereof to among the heaters 1005. Also, the upper surface of the top plate 1001 is provided with an ink supply communication opening 1002 for causing the liquid supplied from the outside to flow into the common liquid chamber 1010. The top plate 1001 is formed of a silicon material, and the pattern of the liquid from paths 1007 and the common liquid chamber 1010 can be formed by etching, and the portions of the liquid flow paths 1007 can be etched and formed after a material such as silicon nitride or silicon oxide which provides the flow path side walls 1001a is accumulated on the silicon substrate by a conventional film forming method such as CVD.
A wall portion is provided on the fore end surface of the top plate 1001, and this wall portion is formed with a plurality of discharge openings 1006 corresponding to the respective liquid flow paths 1007 and communicating with the common liquid chamber 1010 through the liquid flow paths 1007.
FIG. 13 of the accompanying drawings is a partly broken away perspective view showing another example of the liquid discharge head according to the prior art.
The liquid discharge head shown in FIG. 13 is provided with cantilever-like movable members 2009 disposed in face-to-face relationship with heaters 2005. The movable members 2009 comprise thin film formed of a silicon material such as silicon nitride or silicon oxide or nickel or the like excellent in elasticity. These movable members 2009 are disposed at a predetermined distance from the heaters 2005 so as to have fulcrums upstream of the heaters 2005 and further have free ends downstream with respect to these fulcrums.
The top plate 2001, the ink supply communication opening 2002, the packaging electrodes 2003, the substrate 2004, the heaters 2005, the discharge openings 2006, the liquid flow paths 2007 and the common liquid chamber 2013 of the liquid discharge head are similar to those of the liquid discharge head shown in FIG. 12 and therefore need not be described in detail.
FIGS. 14A to 14D of the accompanying drawings are cross-sectional views along the direction of the flow paths for illustrating the liquid discharging method by the liquid discharge head shown in FIG. 13.
As shown in FIG. 14A, when the heater 2005 is caused to generate heat, the heat acts on the ink between the movable member 2009 and the heater 2005, whereby a bubble 2008 based on a film boiling phenomenon is created and grows on the heater 2005. Pressure resulting from the growth of this bubble 2008 preferentially acts on the movable member 2009, which is thus displaced so as to greatly open toward the discharge opening 2006 side about the fulcrum, as shown in FIG. 14B. By the displacement or displaced state of the movable member 2009, the propagation of the pressure based on the creation of the bubble 2008 or the growth of the bubble 2008 itself is directed to the discharge opening 2006 side, and the liquid (liquid droplet 2010) is discharged from the discharge opening 2006, as shown in FIG. 14C.
As described above, the movable member 2009 having a fulcrum on the upstream side (the common liquid chamber side) of the flow of the liquid in the liquid flow path 2007 and having a free end on the downstream side (the discharge opening 2006 side) thereof is provided on each heater 2005, whereby the direction of propagation of the pressure of the bubble 2008 is directed toward the downstream side and thus, the pressure of the bubble 2008 directly and efficiently contributes to discharge. The direction of growth itself of the bubble 2008, like the direction of propagation of the pressure of the bubble, is directed toward the downstream side, and the bubble grows larger on the downstream side than on the upstream side. The direction of the growth itself of the bubble 2008 is thus controlled by the movable member 2009 to thereby control the direction of propagation of the pressure of the bubble 2008, whereby fundamental discharge characteristics such as discharge efficiency and discharging force or discharge speed can be improved.
On the other hand, as shown in FIG. 14D, when the bubble 2008 enters its disappearing step, the bubble 2008 rapidly disappears by the combined effect with the elastic force of the movable member 2009 itself, and the movable member 2009 finally returns to its initial position shown in FIG. 14A. At this time, in order to make up for the contracted volume of the bubble and to make up for the discharged volume of the liquid, the liquid flows from the upstream side, i.e., the common liquid chamber side, and the refilling of the liquid flow path 2007 with the liquid is effected, and this refilling with the liquid is effected efficiently and rationally with the returning action of the movable member 2009.
In a method of manufacturing a liquid discharge head according to the prior art shown in FIG. 15 of the accompanying drawings, movable members 2009 are first formed on a substrate 2004 on which heaters 2005, etc. are provided. The movable members 2009 are made by a series of semiconductor processes comprising, for example, the formation of a sacrifice layer aluminum pattern, the formation of SiN layers forming the movable members 2009 and the patterning of the SiN layers. As described above, devices such as the movable members are provided on the surface of the substrate 2004 and thus, the surface of the substrate 2004 has unevenness of a height of the order of 3 to 10 xcexcm.
Next, a nozzle wall member 2010 for constituting liquid flow paths 2007 and a common liquid chamber 2013 (see FIG. 13 for both) between the substrate 2004 and a top plate 2001 is joined onto the substrate 2004. The upper surface of the nozzle wall member 2010 to which the top plate 2001 is to be joined is then flattened.
Next, the top plate 2001 is joined to the upper surface of the nozzle wall member 2010, and an orifice plate 2011 formed with discharge openings 2006 is joined to an end surface in which the liquid flow paths 2007 open. By the above-described steps, the liquid discharge head according to the prior art shown in FIG. 13 is manufactured.
However, in the manufacturing method described with reference to FIG. 15, it is necessary to accurately join the nozzle wall member 2010 onto the substrate 2004 and further, it is necessary to flatten the upper surface of the nozzle wall member 2010 before the joining of the top plate 2001 and therefore, the manufacturing steps have been cumbersome.
Also, when this wall member is to be formed of an organic material, thick film of the above-mentioned thickness can be formed if dry film is used, but the surface of the substrate is uneven as described above and therefore, not only it has been difficult to achieve the flattening of the upper surface of the wall member, but there has been the fear that the movable members are deformed by the dry film. Further, it has been difficult to form thick film of a thickness of several tens of xcexcm, by the use of the conventional wet process.
So, the present invention has as its object to provide a liquid discharge head in which the upper surface of a wall member can be flattened and the manufacturing time for which can be shortened and which is provided with a wall member formed into thick film having a thickness of several tens of xcexcm, a method of manufacturing the liquid discharge head, a minute mechanical apparatus and a method of manufacturing the minute mechanical apparatus.
To achieve the above object, the liquid discharge head of the present invention is a liquid discharge head having a discharge opening for discharging liquid droplets therefrom, a wall member constituting a liquid flow path communicating with the discharge opening to supply liquid to the discharge opening, a substrate provided with a bubble creating element for creating a bubble in the liquid filling the liquid flow path, and a movable member supported by and fixed to the substrate with the discharge opening side thereof as a free end at a position on the substrate which faces the bubble creating element with a gap between it and the substrate, the free end of the movable member being displaced in a direction opposite to the substrate by pressure produced by creating the bubble, and the pressure being directed to the discharge opening side to thereby discharge the droplet of the liquid from the discharge opening, characterized in that the wall member is constructed by providing and patterning liquid resin of a negative type hardened when exposed to light on a surface on which the movable member is formed.
According to the liquid discharge head constructed as described above, as compared with a case where an inorganic material such as SiN or SiO is formed into film to thereby form a wall member, it becomes possible to shorten the manufacturing time. Further, according to the present invention, the wall member is formed by exposing a predetermined portion of resin of the negative type applied onto the substrate to light to thereby harden it and therefore, unlike the conventional wet process, it becomes possible to form thick film having a thickness of several tens of xcexcm.
Also, preferably the wall member may be of a construction formed by a forming method having the step of applying the liquid resin to that surface of the substrate on which the movable member is provided by spin coating, the step of exposing to light and hardening that portion of the applied resin which constitutes the wall member, and the step of removing that portion of the applied resin which is not hardened.
Further, the forming method has the step of effecting the baking of the resin at a temperature equal to or higher than the melting point of the hardened resin after the step of removing that portion of the applied resin which is not hardened, whereby the levelling flow of the upper surface of the wall member is effected highly accurately. Therefore, it is not necessary to flatten the upper surface of the wall member by polishing or the like which is a post-step, and the manufacturing steps for the liquid discharge head are simplified and further, it becomes possible to manufacture the liquid discharge head inexpensively.
Furthermore, by adopting a construction in which the resin contains a solid component of 50% or more and the average molecular weight thereof is 10,000 or less, the viscosity of the resin becomes relatively low and it becomes possible to flatten the resin well at the applying step by spin coating and also, the resin can be made to flow well into the gap between the substrate and the movable member. Therefore, the possibility of flexure or bending occurring to the movable member when the resin is applied by spin coating can be reduced.
Also, the method of manufacturing a liquid discharge head of the present invention is a method of manufacturing a liquid discharge head having a discharge opening for discharging liquid droplets therefrom, a wall member constituting a liquid flow path communicating with the discharge opening to supply liquid to the discharge opening, a substrate provided with a bubble creating element for creating a bubble in the liquid filling the liquid and flow path, and a movable member supported by and fixed to the substrate with the discharge opening side thereof as a free end at a position on the substrate which faces the bubble creating element with a gap between it and the substrate, the free end of the movable member being displaced in a direction opposite to the substrate by pressure created by creating the bubble, and the pressure being directed to the discharge opening side to thereby discharge the droplet of the liquid from the discharge opening, characterized by the step of using resin of a negative type hardened when exposed to light as a material forming the wall member, and applying the liquid resin to that surface of the substrate on which the movable member is provided by spin coating, the step of exposing to light and hardening that portion of the applied resin which constitutes the wall member, and the steps of removing that portion of the applied resin which is not hardened.
Thereby, as compared with a case where an inorganic material such as SiN or SiO is formed into film to thereby form a wall member, the manufacturing time is shorted and further, unlike the conventional wet process, it becomes possible to form thick film of a thickness of several tens of xcexcm.
Further, there may be adopted a construction having the step of effecting the baking of the resin at a temperature equal to or higher than the fusing point of the hardened resin after the step of removing that portion of the applied resin which is not hardened.
Furthermore, there may be adopted a construction in which the resin contains a solid component of 50% or more and the average molecular weight thereof is 10,000 or less.
Also, the minute mechanical apparatus of the present invention is a minute mechanical apparatus having a first substrate on the surface of which a wall member constituting a liquid flow path is provided, a movable member supported by and fixed to the first substrate with one end portion thereof as a free end with a gap between it and the first substrate in the liquid flow path on the first substrate, and a second substrate joined to the upper surface of the wall member, characterized in that the wall member is constructed by liquid resin of a negative type hardened when exposed to light being provided and patterned on that surface of the first substrate on which the movable member is formed.
Further, preferably the resin may contain a solid component of 50% or more and the average molecular weight thereof may be 10,000 or less.
Also, the method of manufacturing a minute mechanical apparatus of the present invention is a method of manufacturing a minute mechanical apparatus having a first substrate on the surface of which a wall member constituting a liquid flow path is provided, a movable member supported by and fixed to the first substrate with one end portion thereof as a free end with a gap between it and the first substrate in the liquid flow path on the first substrate, and a second substrate joined to the upper surface of the wall member, characterized by the step of using resin of a negative type hardened when exposed to light as a material forming the wall member, and applying the liquid resin to that surface of the substrate on which the movable member is provided by spin coating, the step of exposing to light and hardening that portion of the applied resin which constitutes the wall member, and the step of removing that portion of the applied resin which is not hardened.
Preferably there may be adopted a construction having the step of effecting the baking of the resin at a temperature equal to or higher than the melting point of the hardened resin after the step of removing that portion of the applied resin which is not hardened.